Method to visualize and manufacture aligner by modifying tooth position

ABSTRACT

Orthodontic systems and related methods are disclosed for designing and providing improved or more effective tooth moving systems for eliciting a desired tooth movement and/or repositioning teeth into a desired arrangement. Methods and orthodontic systems include the generation of an overcorrection in the tooth-receiving cavities of an appliance worn in the dentition. The overcorrection may provide an improved and more accurately applied force or moment applied to a tooth. The overcorrected force or moment can move a tooth closer to a desired position than if not overcorrected as sufficient force can still applied to the tooth as it gets closer to the desired position. The overcorrected force or moment may also better target the root of the tooth where the biological response to tooth movement occurs. The overcorrection may be calculated in various ways as described herein.

CROSS-REFERENCE

This application is a continuation of U.S. Pat. Application No.16/576,707, filed Sep. 19, 2019, which is a continuation of U.S. Pat.Application No. 15/684,775, filed Aug. 23, 2017, issued as U.S. Pat. No.10,463,452 on Nov. 5, 2019, which claims the benefit of U.S. ProvisionalApplication No. 62/379,199, filed Aug. 24, 2016, which are incorporatedherein by reference in their entireties.

BACKGROUND OF THE INVENTION

Prior methods and apparatus for aligning teeth can be less than ideal inat least some instances. While braces can be used to move teeth intoalignment, braces can be cumbersome to wear and can require expertise toplace on the subject. Also, complex movements can be difficult toachieve and orthodontic placement may less than ideally address thecomplex movements of several teeth in at least some instances.

Transparent shell appliances have been used to successfully move teeth.For example a user can be provided with a series of transparent shellappliances. Each shell of the series of shells may correspond to a stageof the treatment. For example, a fourth shell in a series of ten shellsmay correspond to the fourth state of treatment. Although transparentshell appliances can be used to successfully reposition teeth, thetransparent shell appliances can provide less than ideal results in atleast some instances. For example, complex movements of teeth, such asto fill an extraction can be difficult to treat with transparent shellappliances. Also, in at least some instances, a wearer of a transparentshell appliance may not complete treatment, for example when teeth donot move sufficiently with the appliance and the user stops treatment.Additionally, in at least some instances, the course of treatment mayneed to be reevaluated as the treatment is implemented, which maynecessitate the manufacture of a second series of transparent shellappliances, prolonging treatment time.

Prior methods and apparatus of aligning teeth with transparent shellappliances can rely on providing shells with cavities shaped to thetooth profile at a final intended position and orientation at a stage ofthe treatment. Work in relation to embodiments suggests cavities shapedto position a tooth at a final intended position and orientation at astage of the treatment can provide less than ideal movement. Althoughattachments can be placed on teeth to facilitate movement of the teethwith polymeric shell appliances, the resulting movements can be lessthan ideal in at least some instances. For example, the force applied tothe tooth can decrease as the tooth moves toward the target position.Also, the movement of a tooth may not be uniform, and the tooth may movemore easily along some dimensions than others. For example, the movementof a tooth can occur along six degrees of freedom, and relative movementcompared to a target movement can differ among the degrees of freedom ofthe tooth. Further, the movement of teeth can be coupled, such thatmovement of a first tooth can affect movement adjacent teeth.

Prior appliances to move teeth may provide teeth receiving cavities atlocations corresponding to the locations of the teeth at the end of eachstage of treatment. This approach can be less than ideal in at leastsome instances.

Although manufacturing appliances in accordance with target positions ofthe teeth at the end of each stage of treatment can be effective, workin relation to embodiments suggests that the amount of force applied toeach tooth can be less than or greater than would be ideal, and thecorresponding movement of the tooth can be less than ideal in at leastsome instances. There can be a discrepancy between the locations of theteeth receiving cavities of the polymeric shell appliance applied andcurrent positions of the teeth. The force and moment may be created fromthe deformation of the polymeric shell appliance put on the teeth. Whena tooth is moved close to its position in the next stage of thetreatment course, the discrepancy between the polymeric shell applianceused and the tooth also can get smaller. Accordingly, the force appliedby the polymeric shell appliance can be also reduced. When the force issmall enough, there may be no tooth movement achieved until the nextpolymeric shell appliance with a new, larger discrepancy is used.Additionally, the force and moment created by the polymeric shellappliance can be from the discrepancy of the crown part of the tooth,and may be applied on tooth crown only, for example. However, thebiological response for tooth movement can be generally centered on thetooth root and not the crown. Therefore, the force from the crowndiscrepancy may be less than ideal for root movement.

In light of the above, it would be desirable to provide improved methodsand apparatus for moving teeth to target positions with polymeric shellappliances. Ideally such methods and apparatus would more accuratelymove teeth to target positions with decreased forces. In someembodiments, the methods, systems, and apparatus would allow dentalpractitioners to view, modify and approve suggested target toothpositions.

SUMMARY

Described herein are embodiments of systems and methods to generatemodified, overcorrected positions for a set of appliances such aspolymeric shell appliances. An “achievement matrix” may be generated bydata analysis of past treated cases to generate the modified,overcorrected positions. Alternatively or in combination, a “forcemoment matrix” may be generated by measuring the force and moment fromthe discrepancy of a particular polymeric shell appliance from the teethof a subject. Alternatively or in combination, a rotational componentmay be added to the pure translation movement of a particular polymericshell appliance to compensate for the tipping effect while moving teeth.

Other objects and features of the present invention will become apparentby a review of the specification, claims, and appended figures.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.U.S. Provisional Application No. 62/119,724, filed Feb. 23, 2015, U.S.Provisional Application No. 62/119,759, filed Feb. 23, 2015, and U.S.Pat. Application No. 15/051,364, filed Feb. 23, 2016, are incorporatedby reference herein in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 shows a schematic of a tooth in a current position, a desiredtarget position, an actual resulting position from the application of aplain polymeric shell appliance, an overcorrected position, and anactual resulting position from the application of a polymeric shellappliance of the present disclosure, according to many embodiments;

FIG. 2 shows a flowchart of a method of manufacturing a set of polymericshell appliances with overcorrection, according to many embodiments;

FIG. 3 shows a graph of the discrepancy between a planned tooth path andan overcorrected tooth path, according to many embodiments;

FIG. 4 shows a schematic of a tooth in a current position, a nextplanned position, and an overcorrected position, according to manyembodiments;

FIG. 5 shows a flowchart of a method of manufacturing a set of polymericshell appliances with overcorrection, according to many embodiments;

FIG. 6 shows a schematic of rotational tooth movement generated by apolymeric shell appliance, according to many embodiments; and

FIG. 7 shows a flowchart of a method of manufacturing a set of polymericshell appliances with overcorrection, according to many embodiments.

FIG. 8A shows a three-dimensional model of a patient’s teeth in a targetposition, according to many embodiments.

FIG. 8B shows a three-dimensional model of a patient’s teeth in anovercorrected position, according to many embodiments.

FIG. 9 shows a three-dimensional model of a patient’s teeth and adigital tool, according to many embodiments.

FIG. 10 shows a three-dimensional model of a patient’s teeth in a targetposition with a three-dimensional model of a patient’s teeth in anovercorrected position, according to many embodiments.

FIG. 11 shows a three-dimensional model of a patient’s teeth in a targetposition with a three-dimensional model of a patient’s teeth in anovercorrected position and a force system, according to manyembodiments.

FIG. 12 shows a three-dimensional model of a patient’s teeth in a targetposition with a three-dimensional model of a patient’s teeth in anovercorrected position and a volume, according to many embodiments.

FIG. 13 shows a three-dimensional model of a patient’s teeth and adigital tool, according to many embodiments.

FIG. 14 shows a three-dimensional model of a patient’s teeth.

DETAILED DESCRIPTION

The present disclosure provides systems and methods to generatemodified, overcorrected positions for a set of appliances such aspolymeric shell appliances.

In one aspect, a system for moving one or more teeth with a dentalappliance is provided. The system comprises a database comprising datacorresponding to one or more of: (1) a plurality of discrepanciesbetween target positions of teeth and achieved positions of the teeth inresponse to treatment, (2) a plurality of correlations between teethmovements and force systems applied by dental appliances, or (3) aplurality of clinical results of achieved teeth movements in response toforce systems applied by dental appliances. The system can comprise aprocessing unit coupled to the database, wherein the processing unit isconfigured to determine an initial position of each of the one or moreteeth, determine a target position for each of the one or more teeth ina treatment plan, and determine a movement vector to move said each ofthe one or more teeth from the initial position to the target positionwith an overcorrected tooth receiving cavity position determined inresponse to the data in the database.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the data corresponds to the plurality ofdiscrepancies, the plurality of discrepancies comprising a discrepancyof one or more of a force system, an achievement matrix, or clinicalknowledge.

In many embodiments, the processing unit is configured to modify one ormore tooth receiving cavity geometries of the dental appliance based onthe overcorrected position.

In many embodiments, the movement vector is configured to establish aforce system applied by the dental appliance to each tooth to move thetooth from the initial position to the target position with theovercorrected tooth receiving cavity position. The force system, whenapplied by the dental appliance, can move the tooth from the initialposition to a position closer to the target position than theovercorrected tooth receiving cavity position. The force system cancomprise one or more of a force, a moment of a force, or a moment of acouple.

In many embodiments, the movement vector is further determined inresponse to one or more of a minimum or maximum vertex distance.

In many embodiments, the processing unit is further configured todetermine an overcorrected tooth receiving cavity corresponding to theovercorrected tooth receiving cavity position, the overcorrected toothreceiving cavity comprising a three dimensional shape profile to receivea corresponding tooth having a corresponding three dimensional shapeprofile, the three dimensional shape profile of the tooth receivingcavity being one or more of rotated or translated relative to thecorresponding three dimensional shape profile of the corresponding toothin the target positon in order to define the overcorrected toothreceiving cavity position.

In many embodiments, the dental appliance comprises a polymeric shellappliance.

In many embodiments, the processing unit is further configured togenerate instructions for fabricating a dental appliance in accordancewith any of the embodiments herein, wherein the dental appliancecomprises a tooth receiving cavity having the overcorrected toothreceiving cavity position. The dental appliance, when positioned on theone or more teeth, can be shaped to move the one or more teeth from theinitial position toward the target position along the movement vector.

In another aspect, a method for determining one or more tooth receivingcavity positions of a dental appliance for moving one or more teeth isprovided. The method can comprise: providing a database comprising datacorresponding to one or more of: (1) a plurality of discrepanciesbetween target positions of teeth and achieved positions of teeth inresponse to treatments, (2) a plurality of correlations between teethmovements and force systems applied by dental appliances, or (3) aplurality of clinical results of achieved teeth movements in response toforce systems applied by dental appliances; determining an initialposition of the one or more teeth; determining a target position of eachof the one or more teeth in a treatment plan; and determining anovercorrected position of one or more tooth receiving cavities of thedental appliance in response to the data in the database.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the data corresponds to the plurality ofdiscrepancies, the plurality of discrepancies comprising a discrepancyof one or more of a force system, an achievement matrix, or clinicalknowledge.

In many embodiments, the method further comprises modifying a geometryof the one or more tooth receiving cavities of the dental appliancebased on the overcorrected position.

In many embodiments, the dental appliance is configured to apply a forcesystem to the tooth to move the tooth from the initial position to thetarget position with the overcorrected tooth receiving cavity position.The force system, when applied by the dental appliance, can move thetooth from the initial position to a position closer to the targetposition than the overcorrected position. The force system can compriseone or more of a force, a moment of a force, or a moment of a couple.

In many embodiments, determining the overcorrected position compriseslimiting the overcorrected position in response to one or more of aminimum or maximum vertex distance.

In many embodiments, the method further comprises determining anovercorrected tooth receiving cavity corresponding to the overcorrectedtooth receiving cavity position, the overcorrected tooth receivingcavity comprising a three dimensional shape profile to receive acorresponding tooth having a corresponding three dimensional shapeprofile, the three dimensional shape profile of the tooth receivingcavity being one or more of rotated or translated relative to thecorresponding three dimensional shape profile of the corresponding toothin the target positon in order to define the overcorrected position.

In many embodiments, the dental appliance comprises a polymeric shellappliance.

In many embodiments, the method further comprises generatinginstructions for fabricating a dental appliance in accordance with anyof the embodiments herein, wherein the dental appliance comprises atooth receiving cavity having the overcorrected tooth receiving cavityposition. The dental appliance, when positioned on the one or moreteeth, can be shaped to move the one or more teeth from the initialposition toward the target position along the movement vector. Themethod can further comprise fabricating the dental appliance.

In another aspect, a system for moving one or more teeth with a dentalappliance is provided. The system can comprise a database comprisingdata corresponding to a plurality of discrepancies between targetpositions of teeth and achieved positions of the teeth in response totreatment, and a processing unit coupled to the database. The processingunit can be configured to determine one or more initial positions of theone or more teeth, determine a target position for each of the one ormore teeth in a treatment plan, and determine a movement vector to movesaid each of the one or more teeth from the initial position to thetarget position with an overcorrected tooth receiving cavity positiondetermined in response to the plurality of discrepancies.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the plurality of discrepancies comprises adiscrepancy of one or more of a force system, an achievement matrix, orclinical knowledge.

In many embodiments, the processing unit is configured to modify one ormore tooth receiving cavity geometries of the dental appliance based onthe overcorrected position.

In many embodiments, the movement vector is configured to establish aforce system applied by the dental appliance to the tooth to move thetooth from the initial position to the target position with theovercorrected tooth receiving cavity position. The force system, whenapplied by the dental appliance, may move the tooth from the initialposition to a position closer to the target position than theovercorrected tooth receiving cavity position. The force system cancomprise one or more of a force, a moment of a force, or a moment of acouple.

In many embodiments, the movement vector is further determined inresponse to one or more of a minimum or maximum vertex distance.

In many embodiments, the processing unit is configured to receive asinput initial positions of each of the one or more teeth and finalpositions of each of the one or more teeth, to determine a plurality ofstages corresponding to a plurality of appliances to move the one ormore teeth from the initial positions to the final positions, todetermine the target position along a movement path of each of the oneor more teeth for each stage and to determine the overcorrected positionof each of the one or more teeth in response to the target positionalong the movement path for each stage.

In another aspect, a system for moving one or more teeth with a dentalappliance is provided. The system can comprise a database comprising aplurality of correlations between teeth movements and force systemsapplied by dental appliances, and a processing unit coupled to thedatabase. The processing unit can be configured to determine an initialposition of the one or more teeth, determine a target position for eachof the one or more teeth in a treatment plan, and determine a movementvector to move said each of the one or more teeth from the initialposition to the target position with an overcorrected tooth receivingcavity position different from the target position in response to theplurality of correlations.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the processing unit is configured to modify one ormore tooth receiving cavity geometries of the dental appliance based onthe overcorrected position.

In many embodiments, the movement vector is configured to establish aforce system applied by the dental appliance to the tooth to move thetooth from the initial position to the overcorrected position. The forcesystem, when applied by the dental appliance, may move the tooth fromthe initial position to a position closer to the target position thanthe overcorrected position. The force system can comprise one or more ofa force, a moment of a force, or a moment of a couple.

In many embodiments, the movement vector is further determined inresponse to one or more of a minimum or maximum vertex distance.

In many embodiments, the processing unit is configured to receive asinput initial positions of each of the one or more teeth and finalpositions of each of the one or more teeth, to determine a plurality ofstages corresponding to a plurality of appliances to move the one ormore teeth from the initial positions to the final positions, todetermine the target position along a movement path of each of the oneor more teeth for each stage and to determine the overcorrected positionof each of the one or more teeth in response to the target positionalong the movement path for each stage.

In another aspect, a system for moving one or more teeth with a dentalappliance is provided. The system can comprise a database comprising aplurality of clinical results of achieved teeth movements in response toforce systems applied by dental appliances, and a processing unitcoupled to the database. The processing unit can be configured todetermine an initial position of the one or more teeth, determine atarget position for each of the one or more teeth in a treatment plan,and determine a movement vector to move said each of the one or moreteeth from the initial position to the target position with anovercorrected tooth receiving cavity position determined in response tothe plurality of clinical results.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the processing unit is configured to modify a toothreceiving cavity geometry of the dental appliance based on theovercorrected position.

In many embodiments, the movement vector is configured to establish aforce system applied by the dental appliance to the tooth to move thetooth from the initial position to the overcorrected position. The forcesystem, when applied by the dental appliance, may move the tooth fromthe initial position to a position closer to the target position thanthe overcorrected position. The force system can comprise one or more ofa force, a moment of a force, or a moment of a couple.

In many embodiments, the movement vector is further determined inresponse to one or more of a minimum or a maximum vertex distance.

In many embodiments, the processing unit is configured to receive asinput initial positions of each of the one or more teeth and finalpositions of each of the one or more teeth, to determine a plurality ofstages corresponding to a plurality of appliances to move the one ormore teeth from the initial positions to the final positions, todetermine the target position along a movement path of each of the oneor more teeth for each stage and to determine the overcorrected positionof each of the one or more teeth in response to the target positionalong the movement path for each stage.

In another aspect, a method for determining one or more tooth receivingcavity positions of a dental appliance for moving one or more teeth isprovided. The method can comprise: providing a database comprising priortreatment data corresponding to a plurality of discrepancies betweentarget positions of teeth and achieved positions of teeth in response totreatments; determining an initial position of the one or more teeth;determining a target position of each of the one or more teeth in atreatment plan; and determining an overcorrected position of the one ormore tooth receiving cavities in response the prior treatment data.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the dental appliance is configured to apply a forcesystem to the tooth to move the tooth from the initial position to theovercorrected position. The force system, when applied by the dentalappliance, can move the tooth from the initial position to a positioncloser to the target position than the overcorrected position. The forcesystem can comprise one or more of a force, a moment of a force, or amoment of a couple.

In many embodiments, determining the overcorrected position compriseslimiting the overcorrected position in response to one or more of aminimum or maximum vertex distance.

In another aspect, a method for moving one or more teeth with a dentalappliance is provided. The method can comprise: providing a databasecomprising a plurality of correlations between teeth movements and forcesystems applied by dental appliances; and determining one or moreovercorrected positions of one or more tooth receiving cavities of thedental appliance in response to the plurality of correlations.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the dental appliance is configured to apply a forcesystem to the tooth to move the tooth from the initial position to theovercorrected position. The force system, when applied by the dentalappliance, can move the tooth from the initial position to a positioncloser to the target position than the overcorrected position. The forcesystem can comprise one or more of a force, a moment of a force, or amoment of a couple.

In many embodiments, determining the overcorrected position compriseslimiting the overcorrected position in response to one or more of aminimum or maximum vertex distance.

In another aspect, a method for determining positions of one or moretooth receiving cavities of a dental appliance for moving one or moreteeth is provided. The method can comprise: providing a databasecomprising a plurality of clinical results of achieved teeth movementsin response to force systems applied by dental appliances; anddetermining an overcorrected position of the one or more tooth receivingcavities in response to the plurality of clinical results of achievedteeth movements in response to force systems applied by dentalappliances.

In many embodiments, the database comprises one or more of patienttreatment histories, orthodontic therapies, orthodontic information, ordiagnostics.

In many embodiments, the dental appliance is configured to apply a forcesystem to the tooth to move the tooth from the initial position to theovercorrected position. The force system, when applied by the dentalappliance, can move the tooth from the initial position to a positioncloser to the target position than the overcorrected position. The forcesystem can comprise one or more of a force, a moment of a force, and amoment of a couple.

In many embodiments, determining the overcorrected position compriseslimiting the overcorrected position in response to one or more of aminimum or maximum vertex distance.

In another aspect, a method for moving teeth of a patient is provided.The method can comprise: providing a first appliance having a firstplurality of overcorrected tooth-receiving cavities to move the teeth tofirst target positions, the first overcorrected tooth receiving cavitieshaving positions different from the first target positions by firstamounts; and providing a second appliance having a second plurality ofovercorrected tooth-receiving cavities to move the teeth to secondtarget positions, the second overcorrected tooth receiving cavitieshaving positions different from the second target positions by secondamounts; wherein the second amounts are less than the first amounts.

In many embodiments, the first amounts comprise a first plurality offirst amounts and the second amounts comprise a second plurality ofsecond amounts, each of the second plurality of second amounts less thana corresponding first amount of the first plurality of first amounts.

In many embodiments, the second overcorrections are provided after thefirst overcorrections. Alternatively, the second overcorrections can beprovided before the first overcorrections.

In many embodiments, the method further comprises providing a thirdappliance having a third plurality of overcorrected tooth-receivingcavities to move the teeth to third target positions, the thirdovercorrected tooth receiving cavities having positions different fromthe third target positions by third amounts, wherein the third amountsare less than the first and second amounts. The third appliance can beprovided before or after the second appliance.

In another aspect, a system for moving teeth of a patient is provided.The system can comprise: a first appliance having a first plurality ofovercorrected tooth-receiving cavities to move the teeth to first targetpositions, the first overcorrected tooth receiving cavities havingpositions different from the first target positions by first amounts;and a second appliance having a second plurality of overcorrectedtooth-receiving cavities to move the teeth to second target positions,the second overcorrected tooth receiving cavities having positionsdifferent from the second target positions by second amounts; whereinthe second amounts are less than the first amounts.

In many embodiments, the first amounts comprise a first plurality offirst amounts and the second amounts comprise a second plurality ofsecond amounts, each of the second plurality of second amounts less thana corresponding first amount of the first plurality.

In many embodiments, the system further comprises a third appliancehaving a third plurality of overcorrected tooth-receiving cavities tomove the teeth to third target positions, the third overcorrected toothreceiving cavities having positions different from the third targetpositions by third amounts, wherein the third amounts are less than thefirst and second amounts.

In another aspect, for a system or a method according to any of theembodiments herein, the one or more teeth comprise a plurality of teeth,and the appliance comprises a plurality of overcorrected teeth receivingcavities.

In another aspect, for a system or a method according to any of theembodiments herein, each overcorrected tooth receiving cavity comprisesa three dimensional shape profile to receive a corresponding toothhaving a corresponding three dimensional shape profile, the threedimensional shape profile of the tooth receiving cavity one or more ofrotated or translated relative to the corresponding three dimensionalshape profile of the corresponding tooth in the target positon in orderto define the overcorrected tooth receiving cavity position.

In another aspect, for a system or a method according to any of theembodiments herein, the overcorrected tooth receiving cavity comprisesan over correction of a three-dimensional shape profile along one ormore of six degrees of freedom of the tooth receiving cavity of saideach of the one or more teeth.

In another aspect, for a system or a method according to any of theembodiments herein, the appliance comprises a polymeric shell applianceand the polymeric shell appliance has been directly manufactured withone or more of 3D printing, stereo lithography, or fused depositionmodeling.

In another aspect, a method for moving one or more teeth is providedcomprising providing a system according to any of the embodimentsherein.

In another aspect, a system or a method according to any of theembodiments herein further comprises instructions for manufacturing thedental appliance.

The methods, systems, and apparatus disclosed herein can be combined inmany ways and may comprise one or more components of known polymer shellappliances. Known shell appliances to reposition teeth may includefeatures to facilitate the predictability of teeth movement. Forexample, such features may include “Active Attachment,” “Activator,”“Pressure Point,” “Bite ramp,” and “Power ridge” available in productsof Align Technology, Inc. of Santa Clara, CA. Such features may dependon adding features to the plain shell appliance and/or the teeth. Forexample, by active attachment with an activator or attachment, moretorque can be created to rotate the canine or premolar. The power ridgemay be used to create torque to move root in buccal-lingual direction.The polymer shell appliance inner surface may then be modified partiallynear the features attached or added to a tooth. However, the majority ofthe surface of the polymeric shell appliance may still be in theoriginal position (i.e., the intended position of the teeth for theparticular stage of treatment) and unchanged. The instant applicationrefers to such a polymeric shell appliance as a “plain polymeric shellappliance.”

As used herein, the terms “target position” and “planned position” areused interchangeably.

As used herein, the terms “patient” and “subject” are usedinterchangeably.

Although reference is made to an appliance comprising a polymeric shellappliance, the embodiments disclosed herein are well suited for use withmany appliances that receive teeth, for example appliances without oneor more of polymers or shells. The appliance can be fabricated with oneor more of many materials such as metal, glass, reinforced fibers,carbon fiber, composites, reinforced composites, aluminum, biologicalmaterials, and combinations thereof for example. The appliance can beshaped in many ways, such as with thermoforming or direct fabrication asdescribed herein, for example. Alternatively or in combination, theappliance can be fabricated with machining such as an appliancefabricated from a block of material with computer numeric controlmachining.

Examples of appliances such as polymeric shell appliances suitable forincorporation in accordance with embodiments of the present disclosuresuitable are described in U.S. App. Ser. No. 12/623,340, filed on Nov.20, 2009, published as US 2010/0138025 on Jun. 3, 2010, entitled“Orthodontic systems and methods including parametric attachments”, andU.S. App. Ser. No. 13/865,091, filed on Apr. 17, 2013, published as US2013/0230818, entitled “Method and system for optimizing dental alignergeometry”, the entire disclosures of which are incorporated herein byreference.

In many instances and for many movements, a plain polymeric shellappliance may work well. Features can be added when there are difficultmovements such as significant rotation, extrusion, or root movement.Even so, the plain polymeric shell appliance itself can still create themajority of force and moment to move the tooth.

A manufacturing process for a plain polymeric shell appliance may be asfollows. First, initial and final teeth positions may be acquired, and amovement path may be generated of all the teeth. Then, additionalfeatures such as attachments, dimples, and ridges may be added to theteeth. A 3D printer may then be used to print the physical mold of theteeth, jaw, and other features. A thin plastic sheet may be thermalformed on the mold. The gingival line may be cut and the polymeric shellappliance may be removed from the mold. Finally, the plain polymericshell appliance may be cleaned and packaged.

In many embodiments, a processor comprises a user input and display fora user to position and orient a plurality of teeth at target positionsand orientations for each stage of a treatment. Alternatively, the usermay input position and orient the plurality of teeth at target finalpositions and orientations for the final stage of a treatment, and theprocessor may determine positions and orientations of the teeth at eachof a plurality of intermediate stages of treatment. The processor mayreceive as input the plurality of initial positions and initialorientations of the teeth. The processor may comprise instructions toposition teeth receiving cavities of the appliance at positions awayfrom the target positions and orientations for each stage of a pluralityof stages of the treatment in order to provide activation energy to theappliance. The processor may comprise instructions to output thepositions of the teeth receiving cavities away from the target positionsand orientations for each stage of the plurality of stages. Theprocessor may comprise instructions to manufacture a plurality ofappliances with indirect manufacturing comprising thermoforming ordirect manufacturing comprising one or more of 3D printing,stereolithography, or fused deposition modeling, for example. In manyembodiments, the processor generates instructions for fabricating one ormore appliances and transmits the instructions to a fabrication machine,e.g., configured to fabricate the appliances using indirectmanufacturing or direct manufacturing, or combinations thereof.

The plain polymeric shell appliance can be made from the tooth positionfrom the initial and final positions. In software, for example, thetooth position can be designed with the following principles in mind.The teeth may not collide with each other in all stages, or else thecourse of treatment can include removal of parts of one or more teeth.Additionally, in some embodiments, teeth are not moved too fast becauseof biological limitations.

Accordingly, the tooth movement path generated for each stage oftreatment can be related to the limit that the tooth can be moved forthe particular stage of treatment. The polymeric shell appliance itself,however, can be used to move the tooth but not to limit tooth movement,for example. The force from a polymeric shell appliance can be createdbecause the appliance can be based on the teeth positioning of the nextstage of treatment and put on the full dentition of the patient in thecurrent stage of treatment.

In this present disclosure, improved methods of creating polymeric shellappliances are provided. Instead of creating a polymeric shell appliancewith teeth receiving cavities corresponding to the position of a toothin the next stage of treatment, the appliance can be created based on amodified, overcorrected tooth position, for example. In this modifiedtooth position, force and moment may be created to move the tooth rootin the desired direction, rather than limiting the tooth to nextposition. A schematic of a modified tooth position for targeting thetooth root is shown in FIG. 1 .

FIG. 1 shows a schematic of a tooth in various positions—a currentposition 102 (e.g., current position 102 a), a desired target position104 comprising the planned location of the tooth at the end of thetreatment stage (e.g., next planned position 104 a), an actual resultingposition 106 from the application of a plain polymeric shell appliance(e.g., an achieved position with no overcorrection 106 a, which mayexhibit lag in the translation and/or tipping relative to the nextplanned position 104 a), an overcorrected position 112 (e.g.,overcorrected position 112 a, which may exhibit more translation tocreate more force and/or rotation to compensate for tipping and to movethe root relative to the next planned position 104 a), and an actualresulting position 114 from the application of a polymeric shellappliance of the present disclosure configured to overcorrect asdescribed herein (e.g., achieved position with overcorrection 114 a,which may be close to or substantially match the next planned position104 a). Because the force and moment generated can decrease as theappliance and tooth discrepancy decreases, there can be a discrepancybetween the desired target position 104 and the actual position 106 thatis achieved. There may be a lag in the translation of the tooth asindicated by the arrow 108. There may be tipping or rotation from theroot as indicated by the arrow 110. According to embodiments of thepresent disclosure, a polymeric shell appliance may be configured withthe tooth receiving cavities of the appliance at locations correspondingto an overcorrected position 112. More translation may be providedversus the uncorrected appliance to create more force. Rotation may beadded to compensate for the tipping effect and move the root. The forceand moment generated can decrease as the discrepancy between applianceand tooth decreases. A discrepancy can remain, however, between theovercorrected position 112 of the tooth receiving cavity and the actualposition 114 that is achieved, as the tooth moves toward the targetposition. The resulting position 114 from the overcorrection can moreclosely match the desired target position 104 in the course oftreatment.

The appliances such as polymeric shell appliances can be configured inone or more of many ways with the overcorrected tooth receiving cavitiesto move one or more teeth as described herein. The tooth comprises atooth profile, such as a three-dimensional shape profile, and the toothreceiving cavity of the polymeric shell appliance may comprise acorresponding internal three-dimensional shape profile to receive thetooth. The position of the shape profile of the tooth receiving cavityof the polymeric shell appliance can be overcorrected in relation to thenext planned position of the tooth. Alternatively or in combination, theorientation of the three dimensional shape profile of the toothreceiving cavity can be overcorrected in relation to the next plannedorientation of the tooth.

The overcorrection with the three-dimensional shape profile of the toothreceiving cavity can be provided along one or more of six degrees offreedom. The overcorrection can be provided along two or more degrees offreedom, for example along one translational and one rotational degreeof freedom. The overcorrection can be provided along three or moredegrees of freedom, for example along two translational and onerotational degree of freedom. The amount of overcorrection along eachdegree of freedom can be determined in response to clinical data, forexample. Additional degrees of freedom of the tooth receiving cavitiescan be overcorrected to move the tooth to the planned position andorientation.

The appliance can be configured to move a plurality of teeth with aplurality of overcorrected tooth receiving cavities at each of aplurality of stages of the treatment as described herein. Each of theplurality of overcorrected tooth receiving cavities can be configured tomove the corresponding tooth of the plurality of teeth to the plannedtarget position.

Referring to FIG. 2 , an exemplary method 200 of creating a polymericshell appliance may be as follows. In a step 202, the initial positionof the teeth of a subject may be acquired and input to a processor. In astep 204, the final, desired position of the teeth of the subject at theend of a course of treatment may be determined and input to a processor.In a step 206, the movement path for each tooth may be designed. Themovement path may be designed such that, at each stage of treatment, theteeth may not collide with each other and may move at a limited speed(e.g., 0.25 mm/treatment stage, which may for example be 2 weeks). In astep 208, the tooth movement from the current stage to next stage ornext several stages may be acquired. In a step 210, the tooth positionof next stage may be modified so sufficient force is created (i.e., thediscrepancy from the current to next stage is sufficiently large) tomove the tooth closely to the desired target position. The modificationof step 210 can be performed with an overcorrection in one or more ofmany ways. For example, the tooth position may be overcorrected asdescribed herein. In a step 212, more root movement may be added tocompensate for the tooth root lagging during the movement, for examplewith overcorrection of one or more of the position or orientation of thetooth receiving cavity. In a step 214, rotation may be added tocompensate and overcome the tipping effect while tooth is in bodilytranslation (e.g., for space closure treatment), for example withovercorrection of one or more of the position or orientation of thetooth receiving cavity. In a step 216, other changes may be applied toimprove the force or moment applied, for example with overcorrection ofone or more of the position or orientation of the tooth receivingcavity. In a step 218, a mold of all teeth in the modified aligner(i.e., overcorrected polymeric shell appliance) tooth position and jawmay be created. Other features such as like attachment and power ridgesmay be added. The mold may be created using 3D printing technology, forexample. In a step 220, a thin plastic sheet may be thermal formed tothe mold to create the aligner or appliance. In a step 222, the gingivalline may be cut from the molded sheet and the aligner or appliance maybe removed from the mold. In a step 224, the aligner or appliance may becleaned and packaged. Alternatively or in combination, the appliance canbe fabricated directly, for example with one or more of 3D printing,stereo lithography, or fused deposition modeling of the appliance, forexample.

Although the above steps show the method 200 of generating a set ofpolymeric shell appliances overcorrected to move teeth in an improvedmanner in accordance with many embodiments, a person of ordinary skillin the art will recognize many variations based on the teachingdescribed herein. The steps may be completed in a different order. Stepsmay be added or deleted. Some of the steps may comprise sub-steps. Manyof the steps may be repeated as often as beneficial to the treatment.

One or more of the steps of the method 200 may be performed withcircuitry as described herein, for example one or more of a processor orlogic circuitry of a computer or a computerized system. The circuitrymay be programmed to provide one or more of the steps of the method 200,and the program may comprise program instructions stored on a computerreadable memory or programmed steps of the logic circuitry, for example.

Aspects of the present disclosure provide several ways to modify thetooth position for the aligner or polymeric shell appliances, which arediscussed herein and as follows. The methods of modifying the toothposition may be applied alone, in various combinations, or in variouscombinations of their component steps or parts.

1. Modify Tooth Position Based on Achievement Statistics

The appropriate overcorrection may be determined using achievementstatistics. Achievement statistics describe the relationship between theachieved and planned tooth movement for post treatment (or in the middletreatment) cases. A tooth can be considered as a rigid body and itsmovement can be described by 6 degrees of freedom (DOFs), or 3translation and 3 rotations. Optionally, the achievement statisticsprovide data corresponding to discrepancies between achieved and plannedtarget positions of teeth in response to treatment.

After the treatment, the teeth are moved to a new position close to theplanned final position, but not exactly the same. The movement from theinitial tooth position to this new position may be called the achievedmovement. The achieved movement can be measured by taking a newimpression and comparing it to the initial impression. Alternatively orin combination, other types of data besides impressions can be used,such as scans or images of the teeth.

The relationship between the planned movement and the achieved movementcan be described by a statistical relationship called aPlanned-Achievement Relation.

The achievement statistics can show coupling among planned movements andachieved movements, and cross-coupling among terms can be used to designthe polymeric shell appliance.

The Planned-Achievement Relation can be estimated by data analysis of alarge number of treated cases. In some embodiments, linear regressionmay be used.

The Planned-Achievement Relation estimated from the after treatmentcases can represent full movement, i.e., from an initial position of theteeth to the final position of the teeth. The Planned-AchievementRelation for a single stage (which may be referred to as a stagePlanned-Achievement Relation) can be computed from the fullPlanned-Achievement Relation when the stage number is known. Theovercorrection can be computed from the Planned-Achievement Relation.From the Planned-Achievement Relation, it can be known that the desiredfinal positions of the teeth may not be fully achieved using a plainaligner or polymeric shell appliance. An overcorrection may be used toamplify and correct the movement.

However, the overcorrection movement can be adjusted more to deal withcomplicated tooth movement. A consideration may be to blend theovercorrection with planned movement. In some embodiments, whentreatment is started, the overcorrection should not be too great becausea greater than necessary overcorrection may apply too great a force tothe root and cause the patient pain and/or discomfort. After severalweeks, teeth may start moving and the bone near the root may get softbecause of the biological response. Then, further overcorrection can beadded. In some embodiments, when the treatment is reaching the finalstage, the overcorrection can be reduced to let the tooth move closer tothe final position, rather than having a larger overcorrection position.

The data from clinical studies can be fit, for example, with a linearregression of the coefficients of the achievement matrix and R2 valuesdetermined.

The change of overcorrection is shown in the overcorrection graph 400 ofFIG. 3 . The graph 400 shows the planned tooth path 402 of one or moreteeth of the subject, and the overcorrected tooth receiving cavity path404 for a plurality of stages of treatment, e.g., 0 (initial prior totreatment), 1, 2, etc. to N, where N is the final stage. The graph 400includes a line for the planned tooth path 402, which can be compared tothe overcorrected tooth path 404. There may be greater overcorrection atearly stage 406 versus at the later stage 408. Each stage has a plannedtooth position of the subject and a corresponding overcorrected toothposition of the tooth receiving cavity of the appliance as shown withthe dashed line of stages 1 and 2, for example. Each of the plurality ofteeth receiving cavities of an appliance for a stage can beovercorrected with reference to the tooth position as described herein.The tooth receiving cavities of the final stage may or may not beovercorrected, and the appliance may be left on the teeth for a longeramount of time to ensure that the teeth have moved to the final targetpositions.

The processing unit as described herein can be configured withinstructions to receive as input initial positions of each of the one ormore teeth and final positions of each of the one or more teeth. Theprocessing unit can be configured with instructions to determine aplurality of stages corresponding to a plurality of appliances to movethe one or more teeth from the initial positions to the final positions.The processing unit can be configured to determine the target positionalong a planned movement path of each of the one or more teeth for eachstage and to determine the overcorrected position of each of the one ormore tooth receiving cavities in response to the target position alongthe movement path for each stage, for example.

The overcorrection may be gradually reduced to none as the treatmentcourse nears completion. Such reduction in the overcorrection may beprovided to allow the soft tissue of the patient to begin to set, forexample.

Improved methods and systems to move teeth by applying such graduallydecreasing overcorrections are provided by the present disclosure. Thepositions of the tooth receiving cavities of the appliance can belocated to provide overcorrection force vectors to the teeth. Forexample, if the target location of the tooth for the present stage islocated 0.2 mm from the position of the immediately prior stage, thetooth receiving cavity can be located 0.3 mm from the position of theprior stage in order to provide overcorrection with the desired forcevector, for example. A first overcorrected force vector may be appliedon teeth to move the teeth to a first target position with a firstovercorrected tooth receiving cavity of a first appliance. The firstovercorrected force vector may have a first overcorrection directed tomove the teeth to a first overcorrected position different from thefirst target position. A second overcorrected force vector may then beapplied on the teeth to move the teeth to a second target position witha second overcorrected tooth receiving cavity of a second appliance. Thesecond overcorrected force vector may have a second overcorrectiondirected to move the teeth to a second overcorrected position differentfrom the second target position. The second overcorrection may be lessthan the first overcorrection and may be applied after the firstovercorrection. A third overcorrected force vector may be applied on theteeth to move the teeth to a third target position with a third overcorrected tooth receiving cavity of a third appliance. The thirdovercorrected force vector may have a third overcorrection directed tomove the teeth to a third overcorrected position different from thethird target position. The third overcorrection may be less than thefirst and second overcorrections. First, second, and/or third shellappliances having first, second, and/or third pluralities oftooth-receiving cavities, for example, may be provided and configured toapply the first, second, and/or third overcorrected force vectors on thetooth, for example. A person of ordinary skill in the art will recognizevariations in one or more of the order, timing or amount ofovercorrection.

Another adjustment may include the minimum and maximum crown movement.In some embodiments, to move the tooth, enough force but not too largeof a force should be applied to the tooth. For an aligner or polymericshell appliance, the force created can be related to the discrepancybetween the aligner or appliance to the tooth. The overcorrectionmovement can be modified as follows and as described herein.

The maximum movement distance for all crown surface points, from thecurrent position to the overcorrection position, can be measured. Thismaximum vertex distance can be bigger than one number, for example, 0.2mm. This distance can be less than another number, for example 0.50 mm.If the distance is too big or small, the overcorrection movement can beincreased or reduced by multiplying the movement vector.

FIG. 4 shows a schematic of tooth positions and is an example of a toothin a current position 502, a planned target position 504, and anovercorrected target position 506. It can be seen that the overcorrectedtarget position 506 can involve more movement than the planned targetposition 504, particularly for root part 508. The greater movement maybe because the root can be normally hard to move so the aligner orpolymeric shell appliance can be manufactured to move root 508 more.

FIG. 5 shows a flow chart of a method 600 of creating a polymeric shellappliance using an “achievement matrix” as described herein and above.In a step 602, after treatment cases for various patients may becollected. In a step 604, impressions of the dentition of the variouspatients may be made before and after the treatment to estimate thetooth movement achieved. In a step 606, the impressions may be matchedto estimate the achieved tooth movement. Alternatively or incombination, other types of data besides impressions can be used, suchas scans or images of the dentition before and after treatment. In astep 608, an achievement matrix may be built using the estimatedachieved tooth movements of the various embodiments. The achievementmatrix may be built using data analysis such as linear regression. In astep 610, the achievement matrix may be inverted to generate theovercorrection matrix. The achievement matrix can be used to correcttooth movement in response to one or more discrepancies. In a step 612,the overcorrection movement for each treatment stage may be generated byacquiring the plan movement vector for each treatment stage andmultiplying by the overcorrection matrix. In a step 614, theovercorrection movement may be adjusted so the maximum vertex movementof the crown is not too small or too large (e.g., greater than 0.2 mmand less than 0.5 mm). In a step 616, the overcorrection movement may beapplied to the current treatment stage to obtain the modified toothposition. In a step 618, an aligner or polymeric shell appliance may becreated from the modified tooth positions of all teeth.

Although the above steps show the method 600 of generating a set ofpolymeric shell appliances overcorrected to move teeth in an improvedmanner in accordance with many embodiments, a person of ordinary skillin the art will recognize many variations based on the teachingdescribed herein. The steps may be completed in a different order. Stepsmay be added or deleted. Some of the steps may comprise sub-steps. Manyof the steps may be repeated as often as beneficial to the treatment.

One or more of the steps of the method 600 may be performed withcircuitry as described herein, for example one or more of a processor orlogic circuitry of a computer or a computerized system. The circuitrymay be programmed to provide one or more of the steps of the method 600,and the program may comprise program instructions stored on a computerreadable memory or programmed steps of the logic circuitry, for example.

2. Modify Tooth Position Based on Clinical and/or Mechanical Knowledge

Another method of generating the overcorrections may be to use clinicaland/or mechanical knowledge based on a history of multiple cases oftreatment to move teeth with aligners or polymeric shell appliances. Theclinical and/or mechanical knowledge can provide information regardingcorrelations between teeth movements and force systems applied by dentalappliances, as well as clinical results of achieved teeth movements inresponse to force systems applied by dental appliances.

For example, when using aligners or polymeric shell appliances to treata premolar extraction case, there may be an undesirable tipping effectof the canine when the space is closed. When the canine is translateddistally, force can be mostly applied to the crown, which can tip thecanine toward the molar. After the treatment is finished, the canineroot may be straight and not aligned well with the other teeth. Tobetter straighten and align the canine root, an attachment may beprovided to the canine to add more torque and compensate for thetipping. Alternatively or in combination, the tooth position may bemodified with some rotation or torque.

Referring to FIG. 6 , to create such a modified position, one may firstdetermine whether premolar extraction or space closure treatment isappropriate. For canines 1002, the root apex may be rotated distally(around the X axis of the crown basis) as indicated by the arrow 1004and lingually (around the Y axis of the crown basis) as indicated by thearrow 1006. The tipping from the distal translation as indicated byarrow 1008 and lingual movement as indicated by arrow 1010 can therebybe compensated. For the activation of a second premolar 1012, the rootapex can be rotated mesially (around the X axis of the crown basis) asindicated by the arrow 1014 and the second premolar can be translateddistally as indicated by the arrow 1016 in the meantime.

Referring to FIG. 7 , a method 1100 of generating an overcorrectedpolymeric shell appliance can be as follows. First, the initial andfinal positions of teeth in the course of treatment may be determined ina step 1102. Then, the tooth movement path may be defined based onclinical limitations in a step 1104, for example, to avoid the toothcollision and velocity (0.25 mm / 2 weeks). From the first toothmovement path, a second tooth movement path may be created in a step1106 and used to generate an aligner or polymeric shell appliance in astep 1108. The limitation(s) of the tooth arrangement in the second pathcan be bigger than that of the first path. For example, tooth collisionmay be allowed, and the velocity can be bigger than 0.25 mm for 2 weeks.

The knowledge to generate the second tooth movement path or arrangementcan be drawn from various sources. In a step 1110, for example, dataanalysis may be performed for past treatment cases. In a step 1112, forexample, the mechanical properties (i.e., the force / torque created) ofvarious aligners or polymeric shell appliances may be measured in alaboratory. In a step 1114, for example, the overcorrection may accountfor attachments to the teeth such as a power ridge and the like. If anattachment is used, the overcorrection can be small because attachmentmay already help engagement and create force. In a step 1116, forexample, previous clinical knowledge may be applied. In a step 1118, theovercorrection or modification from the first to second tooth paths maybe larger for the initial and middle stages of the treatment, whilegetting smaller when the treatment is close to completed so that thefinal tooth arrangement is close to the final position.

In a step 1120, an overcorrected appliance is generated in response toone or more discrepancies as described above.

Although the above steps show the method 1100 of generating a set ofpolymeric shell appliances overcorrected to move teeth in an improvedmanner in accordance with many embodiments, a person of ordinary skillin the art will recognize many variations based on the teachingdescribed herein. The steps may be completed in a different order. Stepsmay be added or deleted. Some of the steps may comprise sub-steps. Manyof the steps may be repeated as often as beneficial to the treatment.

One or more of the steps of the method 1100 may be performed withcircuitry as described herein, for example one or more of a processor orlogic circuitry of a computer or a computerized system. The circuitrymay be programmed to provide one or more of the steps of the method1100, and the program may comprise program instructions stored on acomputer readable memory or programmed steps of the logic circuitry, forexample.

FIG. 8 a shows and embodiment of a three-dimensional model 1200 of atarget position of a patient’s teeth, in particular a lower arch. Thetarget position may be a final target position that represents a desiredfinal positon of the patient’s teeth after treatment or a targetintermediate position of the patient’s teeth at the end of a step orstage of treatment. The three-dimensional model 1200 is created based ona model of the initial position of the patient’s teeth and a dentalpractitioner’s prescription for a target position of the teeth.

A method for producing the incremental position adjustment appliancesfor subsequent use by a patient to reposition the patient’s teeth willbe described. As a first step, a digital data set representing aninitial tooth arrangement is obtained. The digital data set may beobtained in a variety of ways. For example, the patient’s teeth may bescanned or imaged using well known technology, such as X-rays,three-dimensional X-rays, computer-aided tomographic images or datasets, and magnetic resonance images. Methods for digitizing suchconventional images to produce useful data sets are well known. Usually,however, the teeth of the patient are scanned a plaster cast of thepatient’s teeth is obtained by well known techniques and then plastercast is then scanned of the patient’s teeth are scanned directly usingknow techniques.

When the initial data set is obtained from a tooth casting, the castingis digitally scanned by a scanner, such as a non-contact type laser, adestructive scanner, or a contact-type scanner, to produce the initialdata set. The data set produced by the scanner may be presented in anyof a variety of digital formats to ensure compatibility with thesoftware used to manipulate images represented by the data, as describedin more detail below.

Suitable scanners include a variety of range acquisition systems,generally categorized by whether the acquisition process requirescontact with the three-dimensional object being scanned. Somecontact-type scanners use probes having multiple degrees oftranslational and/or rotational freedom. A computer-readable (i.e.,digital) representation of the sample object is generated by recordingthe physical displacement of the probe as it is drawn across the samplesurface.

Conventional non-contact-type scanners include reflective-type andtransmissive-type systems. A wide variety of reflective systems are inuse today, some of which utilize non-optical incident energy sourcessuch as microwave radar or sonar. Others utilize optical energy.Non-contact-type systems that use reflected optical energy usuallyinclude special instrumentation that carry out certain measuringtechniques (e.g., imaging radar, triangulation and interferometry).

One type of non-contact scanner is an optical, reflective scanner, suchas a laser scanner. Non-contact scanners such as this are inherentlynondestructive (i.e., do not damage the sample object), generally arecharacterized by a relatively high capture resolution, and are capableof scanning a sample in a relatively short period of time.

Both non-contact-type and contact-type scanners also can include colorcameras which, when synchronized with the scanning capabilities, providemeans for capturing, in digital format, color representations of thesample objects.

Other scanners, such as destructive scanners produced can also providedetailed and precise information about a patient’s teeth. In particular,a destructive scanner can image areas that are hidden or shielded from arange acquisition scanner and therefore may not be subject to adequateimaging. A destructive scanner gathers image data for an object byrepeatedly milling thin slices from the object and optically scanningthe sequence of milled surfaces to create a sequence of 2D image slices,so none of the object’s surfaces are hidden from the scanner. Imageprocessing software combines the data from individual slices to form adata set representing the object, which later is converted into adigital representation of the surfaces of the object, as describedbelow.

The destructive scanner may be used in conjunction with a laser scannerto create a digital model of a patient’s teeth. For example, a laserscanner may be used first to build a low resolution image of a patient’supper and lower arches coupled with the patient’s wax bite. Thedestructive scanner then may be used to form high-resolution images ofthe individual arches. The data obtained by the laser scanner indicatesthe relation between the patient’s upper and lower teeth which later canbe used to relate to each other the images generated by the destructivescanner and the digital models derived from them.

The destructive scanner can be used to form the digital data set of thepatient’s teeth by milling and scanning a physical model, such as aplaster casting, of the teeth. To ensure a consistent orientation of thecasting throughout the destructive scanning process, a scanning systemoperator pots the casting in potting material and cures the material ina pressure vacuum (PV) chamber to form a mold. The color of the pottingmaterial is selected to contrast sharply with the color of the castingmaterial to ensure the clarity of the scanned image.

A slicing mechanism mills a thin slice from the mold, and then theoptical scanner scans the surface to create a 2D image data setrepresenting the surface. This milling and scanning process is repeateduntil the entire mold is scanned. The resulting output of thedestructive scanning system is a 3D image data set.

A 3D surface model of the patient’s teeth is then created from the dataset using know techniques. Once a 3D model of the tooth surfaces hasbeen constructed, models of the patient’s individual teeth can bederived. In one approach, individual teeth and other components aresegmented to permit individual repositioning or removal of teeth in orfrom the digital data. The teeth in the model may be segmented eithermanually or automatically, as known in the art.

After the tooth components are segmented, a prescription or otherwritten specification provided by the treating professional is followedto reposition the teeth. Alternatively, the teeth may be repositionedbased on the visual appearance or based on rules and algorithmsprogrammed into the computer. Once an acceptable final arrangement hasbeen created, the final tooth arrangement is incorporated into a finaltarget data set.

Based on both the initial data set and the final target data set, aplurality of intermediate data sets are generated to correspond tosuccessive intermediate tooth arrangements. The system of incrementalposition adjustment appliances can then be fabricated based on theintermediate data sets, as described in more detail below.

The system can be configured to add roots and hidden surfaces to thetooth models to allow more thorough and accurate simulation of toothmovement during treatment. In alternative implementations, thisinformation is added automatically without human assistance,semi-automatically with human assistance, or manually by human operator,using a variety of data sources.

In some embodiments, 2D and 3D imaging systems, such as x-ray systems,computed tomography (CT) scanners, and MRI systems, are used to gatherinformation about the roots of the patient’s teeth. For example, several2D x-ray images of a tooth taken in different planes allow theconstruction of a 3D model of the tooth’s roots. Information about theroots is available by visual inspection of the x-ray image and byapplication of a computer-implemented feature identification algorithmto the x-ray data. The system adds the roots to the tooth model bycreating a surface mesh representing the roots. Physical landmarks onthe patient’s teeth, e.g., cavities or cusps, are extracted from the 2Dand 3D data and are used to register the roots to the tooth model. Likethe roots, these landmarks can be extracted manually or by use of afeature detection algorithm.

Another alternative for the addition of roots and hidden surfaces is tomodel typical root and crown shapes and to modify the digital model ofeach tooth to include a root or a hidden surface corresponding to atypical shape. This approach assumes that the roots and hidden surfacesof each patient’s teeth have typical shapes. A geometric model of eachtypical shape is acquired, e.g., by accessing an electronic database oftypical root and crown models created before the analysis of aparticular patient’s teeth begins. Portions of the typical root andcrown models are added to the individual tooth models as needed tocomplete the individual tooth models.

Yet another alternative for the addition of roots and hidden surfaces isthe extrapolation of the 3D tooth model to include these features basedon observed characteristics of the tooth surfaces. For example, thesystem can use the curvature of a particular molar between the tips ofthe cusps and the gumline to predict the shape of the roots for thatmolar. In other implementations, x-ray and CT scan data of a patient’steeth are used to provide comparison points for extrapolation of thepatient’s roots and hidden surfaces. Models of typical root and crownshapes also can be used to provide comparison points for root and hiddensurface extrapolation.

After the teeth have been placed or removed to produce a model of thefinal tooth arrangement, a treatment plan is generated. The treatmentplan includes the series of intermediate tooth position data sets. Toproduce these data sets, the movement of selected individual teeth aredefined or mapped from the initial position to the final position over aseries of successive steps. In addition, other features may be added tothe data sets in order to produce desired features in the treatmentappliances. For example, it may be desirable to add wax patches to theimage in order to define cavities or recesses for particular purposes,such as to maintain a space between the appliance and particular regionsof the teeth or jaw in order to reduce soreness of the gums, avoidperiodontal problems, allow for a cap, and the like. Additionally, apractitioner may wish to provide a receptacle or aperture intended toaccommodate an anchor which is to be placed on a tooth in order topermit the tooth to be manipulated in a manner that requires the anchor,e.g., to be lifted relative to the jaw.

After the treatment plan is created or the final target position of thepatient’s teeth is determined, a three-dimensional model of thepatient’s teeth in a target position may be displayed. Athree-dimensional GUI is advantageous for both component manipulationand for display to both the patient and dental practitioner.

Such an interface provides the treating professional or user withinstant and visual interaction with the digital model components. Beforeor during the manipulation process, one or more tooth components may beaugmented with template models of tooth roots. The componentmanipulation software is designed to operate at a sophisticationcommensurate with the operator’s training level. For example, thecomponent manipulation software can assist a dental practitioner byautomatically overcorrecting a final target position of a patient’stooth for use in generating an appliance such that the final targetposition is more likely to be achieved.

In some embodiments, the final target potions of the patient’s teeth,also referred to as a clinical goal, are displayed to the dentalpractitioner, for example, as shown in FIG. 8 a , which shows a digitalmodel 1200 of a patient’s lower arch and with a patient’s tooth 1202 ina target position 1204. A dental practitioner experienced in the fieldof teeth repositioning with aligners may manipulate the target positionof the patient’s teeth based on their own experience with aligners, inorder to apply their own overcorrection. Such manual overcorrection,when combined with the overcorrection applied based on one or more ofthe methods discussed above, may result in the patient’s teeth reachingan undesired final position at the final stage of treatment. In someembodiments, the system may generate instructions for generating ordisplaying the three-dimensional model of the patient’s teeth in aninitial position.

To help guide the dental practitioner in developing a target position ofa patient’s teeth, the three-dimensional GUI may also display athree-dimensional model of the overcorrected position of the patient’steeth. For example, FIG. 8 b shows a three-dimensional model 1250 of thelower arch of a patient’s teeth that includes the tooth 1202 in a finalovercorrected position 1252. In this way, a dental practitioner is madeaware of both the target position of the patient’s teeth and theovercorrected position of the patient’s used in manufacturing thealigners. In some embodiments, the system may generate instructions forgenerating or displaying the three-dimensional model of the patient’steeth in a target position.

In some embodiments, a doctor may manipulate teeth in one or both of thetarget position model 1200 and the overcorrected model 1250. In suchembodiments, a change made in one of the models may be reflected in theother model. For example, a dental practitioner may adjust the targetposition 1204 of the patient’s tooth 1202. This adjustment may result inchanges to the overcorrected position 1252 of the patient’s tooth 1202in the overcorrected model 1250. Therefore, in some embodiments, theovercorrected model 1250 may be updated to reflect the changes suchchanges. In some embodiments, such changes occur in real-time or nearreal-time, such as during the same viewing session. In some embodiments,the system may generate revised instructions for generating ordisplaying the three-dimensional model of the patient’s teeth in anovercorrected or overengineered position.

As another example, a practitioner may instead desire to adjust theposition 1252 of the tooth 1202 in the overcorrected model. In such anembodiment, the target position 1204 of the tooth 1202 in the targetmodel 1200 may change to reflect a new target position that is based onthe new overcorrected position. In other embodiments, a practitioner maymake adjustments or refinements to the position 1252 of the tooth 1202in the overcorrected model 1250, but not have such changes reflected inthe target model. For example, the practitioner’s adjustments may bemade to the overcorrected model 1250 based on the practitioner’sexperience with aligners in a particular situation and based on thatexperience, the practitioner provides instructions for a differentovercorrected position in order to reach the same target position.

FIG. 9 shows an example of the six degrees of freedom about which atooth’s position may be moved. In some embodiments, a practitioner mayuse one or more digital tools 1290 to manipulate the target position1274 or the overcorrected position 1278 of the tooth 1272. For example,as shown in FIG. 9 the tooth position may be displaced along thefacial-distal axis 1280, the mesial-distal axis 1282, or theincisal-root axis 1284 and may also be rotation around one or more ofthe axis 1280, 1282, 1284.

In some embodiments, rather than or in addition to displaying the targetposition and overcorrected position as separate, spaced apart digitalmodels, the target positon model and the overcorrected model may beoverlaid or superimposed over one another. For example, FIG. 10 shows atarget model 1300 of a patient’s tooth 1302 in a target position 1304and also shows the overcorrected position 1354 of the patient’s tooth1302.

In some embodiments, the force and moment created by the deformation ofthe polymeric shell appliance while it is on the teeth may be shownalong with the target position model, the overcorrected position model,or both models. For example, FIG. 11 shows an embodiment of a targetmodel 1400 of a patient’s tooth 1402 in a target position 1404 alongwith the overcorrected position 1454 of the patient’s tooth 1402 andalso depicts the force 1408 and moment 1410 applied to the tooth 1402based on the overcorrected position 1452 of the tooth 1402. The forceand moment caused by the deformation of polymeric shell appliance can becomputed by mathematical model or simulation, including, for example,VILab simulation or finite element analysis (FEA) of the shelldeformation. The force and moment can also be measured via mechanicaltest of the aligner on a mold of a patient’s teeth, or for example, anFMA test. The visualization of the force 1408 and moment 1410 aides thepractitioner in determining the appropriate overcorrection for reachingthe desired target position.

Referring now to FIG. 12 , a visualization of a volume 1500 around atarget position 1504 of a tooth 1502 may define a limited zone aroundthe tooth 1502 is shown. In some embodiments, for example, the targetvolume may indicate to the practitioner one or more of a manufacturingzone, a safety zone, a treatment threshold, an aligner fit threshold,and a prediction of the off-track position of a tooth. One such zone isa safety zone. A safety zone is the maximum discrepancy (e.g.,displacement) of one or more feature points on the tooth between thefeature’s location when the tooth is in a target position and when thetooth is in an overcorrected position. For example, the discrepancy of acrown center on a tooth should be less than 1 mm. As another example,the rotation around Z-axis should be less than, for example 10 degrees.Another example is an aligner fit threshold, which can be tested andverified using mechanical experiments like FMA. For example, in an FMAtest of an aligner fit threshold, if the extrusion is set to a largequantity, such as 1 mm, and an attachment on a tooth does not engage toa shell, then no extrusion force is created and the aligner fitthreshold should be 1 mm or less. As another example, a prediction ofoff-track position is a zone representing possible final positions ofthe tooth and may be considered a tolerance around the prediction forthe treatment.

Although the visualizations discussed above have been described withreference to target and overcorrected final and intermediate positionsof a patient’s teeth, such visualizations of models of a patient’s teethmay also be applied in embodiments of tooth movements including stagedmovements of patient’s teeth and in aligner shape modifications.

For example, referring now to FIG. 13 , an embodiment of an alignershape modification is shown. The overcorrected position 1652 of thetooth 1602 is shown with a modification 1610 to the surface of the toothusing a digital tool 1690. Such modifications 1610 may include a cavityfacing dimple, as shown in FIG. 13 , or other shapes such as a lineardimple (ridge), a large cavity covering most of a tooth surface(pressure area), or a localized offset alleviating contact betweenaligner and tooth (bubble). When the aligner is formed based on theovercorrected position 1652 and modifications 1610 to the shape of thetooth the aligner may apply a set of forces and moments to the tooth1602. Such forces and moments may also be depicted, for example asexplained with reference to FIG. 11 .

In some embodiments, the displacements of the tooth receiving cavitiesas compared to the tooth positions may be shown along. For example, FIG.14 shows an embodiment of a model 2000 of a patient’s teeth in aposition along with indicators of the translation and rotationdisplacements of the tooth receiving cavity as compared to the toothposition the patient’s tooth. The translation indicators 2012, 2014,2014 show the relative magnitude and direction of the displacement of atooth receiving cavity as compared to the position of the tooth at astage of treatment in three axis, such as the orthogonal x,y,ztranslation, x,y,z rotation axis of three dimensional Cartesiancoordinate systems. The indicators may also show translation androtations according to a tooth or oral axis, for example, indicator 2012indicates translation in the extrusion-intrusion direction, indicator2014 indicates translation in the buccal-lingual direction, and arrow2016 shows side-to-side translation along the arch of the teeth.Rotational indicators 2010, 2018 show rotational movement aboutrespective axis, for example, indicator 2018 shows rotation about thebuccal-lingual axis while 2010 shows rotation about the side-to-sidearch directional axis. Rotational indicators may also indicate rotationabout the extrusion-intrusion axis. The visualization of the translationand rotation aides the practitioner in determining the appropriateovercorrection for reaching the desired target position.

The depiction of overengineering of the position and shape of apatient’s tooth, including overcorrection, staging, shape, etc, may beapplicable to all phases of treatment of a patient’s tooth. For example,the visualizations may be used during development of the initialtreatment plan, during progress tracking, during adaptive treatmentplanning, during the development of additional aligners, and otherstages of treatment.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1-2. (canceled)
 3. A non-transitory computing device readable mediumstoring instructions executable by a processor to cause a computingdevice to perform a method, the method comprising: determining a targetposition for at least one tooth of a patient’s teeth as part of anorthodontic treatment plan; accessing a database comprisingovercorrection data, wherein the overcorrection data comprisesdiscrepancies between force systems applied during an orthodontictreatment and actual teeth positions achieved as a result of theorthodontic treatment; determining an overcorrection position for the atleast one tooth, wherein the overcorrection position is determined basedat least in part on the overcorrection data, and wherein theovercorrection position is determined to facilitate movement of the atleast one tooth towards the target position; determining a geometry of adental appliance, wherein the geometry comprises a plurality tooth ofreceiving cavities, and wherein the geometry is determined to urge theat least one tooth towards the overcorrection position; and generatinginstructions for fabrication of the dental appliance in accordance withthe determined geometry.
 4. The non-transitory computing device readablemedium of claim 3, wherein the overcorrection position is different fromthe target position.
 5. The non-transitory computing device readablemedium of claim 3, wherein the instructions for fabrication of thedental appliance comprises direct fabrication.
 6. The non-transitorycomputing device readable medium of claim 3, wherein the geometrydetermined to urge the at least one tooth towards the overcorrectionposition is configured to apply a force system.
 7. The non-transitorycomputing device readable medium of claim 6, wherein the applied forcesystem is configured to move the at least one tooth from an initialposition to a position closer to the target position than theovercorrected position.
 8. The non-transitory computing device readablemedium of claim 6, wherein the applied force system is configured tomove the at least one tooth closer to the target position than achievedby a corresponding plain polymeric shell appliance force system.
 9. Thenon-transitory computing device readable medium of claim 3, whereindetermining the target position for the at least one tooth comprisesdetermining a target tooth root position.
 10. The non-transitorycomputing device readable medium of claim 9, wherein the geometrydetermined to urge the at least one tooth towards the overcorrectionposition is configured to apply a force system, and wherein the appliedforce system is configured to move the root of the at least one toothtoward the target tooth root position.
 11. The non-transitory computingdevice readable medium of claim 10, wherein the applied force system isconfigured to compensate for tooth root lagging.
 12. The non-transitorycomputing device readable medium of claim 10, wherein the applied forcesystem is configured to compensate for a tipping of the at least onetooth.
 13. The non-transitory computing device readable medium of claim10, wherein the applied force system is configured to not cause pain ordiscomfort to the patient.
 14. The non-transitory computing devicereadable medium of claim 3, wherein the method further comprisesreceiving initial position information of the at least one tooth. 15.The non-transitory computing device readable medium of claim 14, whereinthe initial position information comprises information about the root ofthe at least one tooth.
 16. The non-transitory computing device readablemedium of claim 15, wherein the information about the root comprises adigital tooth model with at least one root.
 17. The non-transitorycomputing device readable medium of claim 15, wherein the informationabout the root comprises a digital model having a typical root or atypical hidden surface.
 18. The non-transitory computing device readablemedium of claim 14, wherein the initial position information comprises ascan of the patient’s teeth.
 19. A non-transitory computing devicereadable medium storing instructions executable by a processor to causea computing device to perform a method, the method comprising:determining a target position for at least one tooth of a patient’steeth as part of an orthodontic treatment plan; accessing a databasecomprising overcorrection data, wherein the overcorrection datacomprises discrepancies between force systems applied during anorthodontic treatment and actual teeth positions achieved as a result ofthe orthodontic treatment; determining an overcorrection position forthe at least one tooth, wherein the overcorrection position isdetermined based at least in part on the overcorrection data, andwherein the overcorrection position is determined to facilitate movementof the at least one tooth towards the target position; determininggeometries of a plurality of dental appliances, wherein the geometrieseach comprise a plurality of tooth-receiving cavities, and wherein thegeometries are determined to urge the at least one tooth towards theovercorrection position; and generating instructions for fabrication ofthe plurality of dental appliances in accordance with the determinedgeometries.
 20. The non-transitory computing device readable medium ofclaim 19, wherein the overcorrection position is different from thetarget position.
 21. The non-transitory computing device readable mediumof claim 19, wherein the instructions for fabrication of the dentalappliance comprises direct fabrication.
 22. The non-transitory computingdevice readable medium of claim 19, wherein determining the targetposition for the at least one tooth comprises determining a target toothroot position.